1. Technical Field
A method of fabricating an image sensor is disclosed wherein the image sensor is equipped with a lens which can form an image sensor device during the fabrication process of a semiconductor device. The method attaches a lens directly onto the device without assembling a separate lens module.
2. Description of the Related Art
An image sensor is an apparatus which senses information of a subject and converts it into an electrical video signal and is divided into a pickup tube and a solid state image sensor. The former includes a vidicon and a plumbicon, while the latter includes a Complementary Metal Oxide Semiconductor (hereinafter, xe2x80x98CMOSxe2x80x99), a Charged Coupled Device (hereinafter, xe2x80x98CCDxe2x80x99). Among them, the image sensor used as the solid state image sensor is generally used by coupling a lens to a semiconductor chip package equipped with a semiconductor chip for an image sensor. Semiconductor chip packages for an image sensor are broadly classified into those for CMOS and those for CCD according to the semiconductor device.
For a CMOS image sensor, a CMOS and pixel formation process is carried out and finally a metal wire is formed. Then, a color filter formation process is performed in order to embody a color sensor and a micro lens is formed on an upper portion of an individual pixel on an upper portion of a device in order to increase a light gathering power. Next, the device is packaged, and then the packaged device is placed onto a plastic circuit board (hereinafter, xe2x80x98PCBxe2x80x99) and is coupled to a lens module.
Such a method of fabricating an image sensor in the prior art has a problem in that, since the device and the lens module are separate, the focal distance between a pixel array of the device and the lens module needs to be corrected, the shape of the lens module has to be changed according to the position of the pixel array in the device and the size of the lens module has to be changed according to the size of the package.
Additionally, the upper portion of the device can be contaminated by impurities during packaging of the device, defects caused from separation can be generated during assembly of the packaged device and the lens module, and the size of the end product is larger because of the overall size of the module.
Moreover, in the packaging process of the device as well as wafer processing, yield checking and wafer back surface grinding, if impurities remain on the pixel array, defects can be generated. Further, impurities in the package or silicon powders generated on the periphery of the device during cutting can penetrate into the pixel array causing defects.
To solve the above problems, methods of fabricating an image sensor are disclosed wherin the image sensor is equipped with a lens which can attach a lens directly on a device without fabricating a separate lens module in a fabrication process of an image sensor device by forming a concave groove on the bottom surface of the lens and coupling the device and the lens by alignment marks after forming a metal convex portion around a pixel array and forming a lens from a mobile material in the final step of device fabrication prior to performing a packaging process.
One disclosed method of fabricating an image sensor equipped with a lens, wherein a pixel array portion and a CMOS logic portion are integrated into one chip, comprises forming a metal wire and depositing an insulating film and a top metallic layer on a substrate; remaining the top metallic layer around a pixel array and depositing protection films on the top metallic layer; exposing the top metallic layer between the protection films by carrying out a color filter formation process and then a masking process opening a pad metal terminal; depositing a titanium film and a metallic film onto the upper portion of the top metallic layer; opening the portion in which a metal convex portion is to be formed and forming the metal convex portion on the upper portion of the metallic film using an electroplating method; removing the metallic film and the titanium film around the metal convex portion; forming a lens to be aligned with the pixel array of a device; and coupling the device and the lens using alignment marks.
In an embodiment, the titanium film and the metallic film are deposited by a sputtering method or electroplating method.
Preferably, the metallic film and the metal convex portion are made of Au, Ag or Cu. The metal convex portion forming step using the electroplating method is performed using a sulfite electrolyte solution. The top metallic layer remaining around the pixel array can be formed in a closed-type, a streamlined-type or a straight-type. The lens has a groove which can be integrated with the metal convex portion.